Orthopedic sawing procedures may result in incorrect saw lengths or damage to a patient (i.e., if the sawing action continues after cut completion or if an incorrect cut depth is made), which can lead to surgical complications. Furthermore, in cases where the length of a cut made using a surgical saw is to be determined, determining the length for a cut can be a time consuming procedure which is undesirable when tissue is exposed and potentially subjected to infection.
As shown in FIG. 1, a cross section of a bone 10 having with a hard cortex 12 is shown. The bone 10 may be surrounded by a medium 14 that is less dense than the hard cortex 12 (e.g., soft tissue or air in the case of a bone exposed during a surgical procedure). In orthopedic procedures, it may be necessary to saw a bone 10 (e.g., saw a portion of a bone or completely through a bone). When cutting through all or a portion of a bone 10, failure to arrest oscillation of the saw blade as soon as a cut is complete may result in unnecessary damage to the area around the cut. Furthermore, precise control over the depth of a cut may be needed in certain surgical operations.
Previously proposed techniques for sawing include the surgeon making a cut through the bone until the surgeon “feels” the saw blade pass completely through the bony structure or have the surgeon estimate a depth of the cut during the cutting operation. That is, the surgeon must rely on his or her senses and judgment alone to determine when the saw blade has passed completely through the bony structure or to a predetermined depth. Once the surgeon believes that he or she has passed completely through the structure or to the predetermined depth, the saw blade oscillation is arrested by the surgeon. Thereafter the surgeon may measure the length of the cut. A possible resulting complication of this procedure is that the surgeon may mistakenly “feel” the saw blade pass through a layer of differing density, thus falsely believing the cut to be complete. Additionally, the surgeon may not precisely “feel” the saw blade pass through the bone, thereby possibly damaging tissue on the opposite side of the bone.
Additionally, it may be necessary of a surgeon to measure the cut length once the cut is complete or stop cutting at a prescribed length that was predetermined by imaging software or a measurement jig. However, access to the anatomy that is cut may be limited, thus also limiting the ability to use such measurement jigs or other fixtures to control the depth of a cut. As such, traditional measurement techniques for verification of the cut length may be subject to error. As such, the process of sawing to a measured depth often includes inaccurate guess work. Conservative sawing may result in incomplete sawing (i.e., failure to saw completely through the bone or failure to saw to a predetermined depth), thus requiring multiple attempts. As such, sawing to a predefined depth is quite difficult. Additionally, it may be difficult to quickly arrest the saw blade motion upon cut completion. As such, the process may consume a substantial amount of surgical time resulting in a large cost per patient. By combining the sawing and depth measurement process into one accurate procedure, cost is reduced along with a decrease in patient morbidity.